1. Field of the Invention
The present invention relates to an apparatus and method for diagnosing sleep apnea. More particularly, the present invention relates to an apparatus and method for detecting whether a temporary absence or cessation of breathing occurs while a subject is sleeping by applying light of two different wavelengths to a predetermined part of the subject's body.
2. Description of the Related Art
Sleep apnea is a temporary absence or cessation of breathing during sleep, thereby causing oxygen to cease entering the body. In general, when no oxygen enters the body due to sleep apnea, an oxygen saturation, i.e., an amount of oxygen in the blood, decreases to an abnormal level.
Sleep fragmentation at night due to sleep apnea causes excessive daytime sleepiness (EDS) and a decline in arterial oxygen saturation. A decline in oxygen saturation may cause high blood pressure, arrhythmia, or the like. Occasionally, a decline in oxygen saturation may even have fatal results by causing a heart attack while a person is sleeping. It is reported that about 20 percent of the adult population of the United States suffers from snoring, and about 50 percent of those people that snore suffer from sleep apnea.
Children with sleep apnea show such symptoms as decreased attention span, erratic behavior, EDS, irregular sleep, rib cage retraction, and flaring of the ribs. Such children may do poorly in an academic setting and, in the most serious cases, may suffer from mental or psychological disorders. For infants or babies, sleep apnea may cause sudden death during sleep.
Sleep apnea is typically classified into three main types: obstructive, central, and mixed. Obstructive sleep apnea is the most common form of sleep apnea and is characterized by a repeated closing of an upper airway. Central sleep apnea occurs when the brain fails to send adequate signals to the diaphragm and lungs during sleep, thereby resulting in decreased respiration. Mixed sleep apnea is a combination of obstructive sleep apnea and central sleep apnea. Regardless of the type of sleep apnea, sleep apnea results in a decrease in arterial oxygen saturation.
A breathing disorder is clinically classified as sleep apnea when a cessation of breathing lasting for ten or more seconds occurs at least five times an hour or at least thirty times during in a seven-hour period. Snoring is a sound made when a soft palate of the upper airway vibrates, and thus, is often a direct precursor of sleep apnea.
A sleep apnea test is generally performed through polysomnography. Polysomnography is a test during which sleep architecture and function and behavioral events during sleep are objectively measured and recorded. More specifically, a number of physiological variables, such as brain waves, eye movement, chin electromyogram, leg electromyogram, electrocardiogram, snoring, blood pressure, breathing, and arterial oxygen saturation, are measured extensively. At the same time, behavioral abnormalities during sleep are recorded with video tape recorders. Trained technicians and sleep specialists read the record to obtain comprehensive results about the severity of snoring, whether arrhythmia occurs, whether blood pressure increases, whether other problems are caused during sleep, and at what points the record differs from normal sleep patterns.
Conventional apparatuses and methods for diagnosing sleep apnea have several disadvantages including being difficult to implement, being unable to detect all three types of sleep apnea, being unable to provide accurate and reliable results, and causing discomfort in a subject being monitored.